12题……过程?
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12题……过程?12题……过程? 12题……过程?y=cos^2x-3sinx+2=1-sin^2x-3sinx+2=-(sin^2x+3sinx)+3=-(sin^2x+3sinx+9/4
12题……过程?
12题……过程?
12题……过程?
y=cos^2x-3sinx+2
=1-sin^2x-3sinx+2
=-(sin^2x+3sinx)+3
=-(sin^2x+3sinx+9/4)+3+9/4
=-(sinx+3/2)^2+21/4
最大值是当sinx=-1时
y最大=-(-1+3/2)^2+21/4
=-1/4+21/4
=5
选C